The present invention relates to check valves and also to check valves used in cooler bypass assemblies which only permit fluid flow to a cooler when the temperature of the fluid is above a certain temperature.
Check valves are mounted in bores in a housing or other element and have a movable member, such as a ball, which is movable into and out of engaged sealing engagement with a valve seat formed in the bore to open or close off fluid flow through the bore while allowing the fluid, when flowing, to flow in only one direction through the bore. A spring exerts a biasing force on the movable member or ball to normally bias the ball into engagement with the valve seat to close off fluid flow through the bore.
When the fluid pressure in the bore increases to a magnitude greater than the spring force, the fluid pressure overcomes the spring force and moves the ball away from the valve seat. This opens the bore to through flow of fluid from the bore inlet to the bore outlet. When the fluid pressure decreases below the spring force, the spring moves the ball back into engagement with the valve seat to close off fluid flow through the bore.
However, oscillation of the movable member or ball can occur when the ball rapidly reciprocates into and out of engagement with the valve seat creating objectionable noise and valve chatter. This occurs just after the ball disengages from the valve seat as fluid flow past around the ball creates a momentary pressure equalization on both sides of the ball. This momentary pressure equalization relieves the pressure acting to force the ball against the spring and allows the spring to move the ball back toward the valve seat. The reciprocating movement of the ball into and out of engagement with the valve seat causes in the objectionable valve chatter.
It would be desirable to provide a check valve which minimizes valve chatter resulting from oscillation of the movable valve member into and out of engagement with the valve seat; while still enabling proper operation of the check valve.